Fe-C-Mn-Si TRIP钢经配分处理后显微组织的TEM观察

相变诱发塑性钢（TRIP钢）是一种优良的汽车用钢，本文利用一种新的热处理工艺：淬火和配分处理相结合的工艺对Fe-0.2C-1.5Si-1.67Mn TRIP钢进行热处理。经过淬火和配分处理所得到的Fe-0.2C-1.5Si-1.67Mn配分钢的抗拉强度为1100MPa，而同样成分的TRIP钢的抗拉强度只有800MPa，且相对于TRIP钢而言，配分钢在抗拉强度提高的同时塑性和韧性仍然可达到20%。     

利用原子力显微镜鉴别相变诱发塑性钢的显微组织

相变诱发塑性（TRIP）钢比双相钢具有更高强度和塑性，因此TRIP钢在汽车工业中的应用对于汽车轻量化有重要的经济意义。TRIP钢的高强度和高延展性主要来源于钢中复杂的显微组织以及应变条件下亚稳态的残余奥氏体（A1）向马氏全（M）的转变，即相变诱发塑性。钢中各相组织的正确鉴别显得尤为重要，特别是钢中残余奥氏体的含量、分布及其稳定性直接关系到TRIP钢性能的好坏。根据目前使用的常规鉴别方法、     

马氏体钢亚晶结构的TEM研究

现代马氏体钢Ｇ Ｘ12ＣｒＭｏＶＮｂＮ 10 1 1作为耐热抗形变材料广泛用于发电工业。钢的蠕变强度是和其微结构密切相关的[1] 。本文报道用ＴＥＭ定量研究退火和蠕变过程中马氏体钢亚晶结构变化的实验结果。实验所用材料为铸造马氏体钢Ｇ Ｘ12ＣｒＭｏＶＮｂＮ 10 1 1,其化学成份 (ｗｔ .% ,ｂａｌ .Ｆｅ)为0 13Ｃ、0 2 9Ｓｉ、0 82Ｍｎ、9 5 1Ｃｒ、1 0 2Ｍｏ、0 0 5 9Ｎｂ、0 5 2Ｎｉ、0 19Ｖ、1 0 2Ｗ、0 0 14Ｐ、0 0 4 14Ｎ、0 0 14Ａｌ。材料的初始态由热处理确定 ,其过程为 1343Ｋ 12ｈ ,空冷 + 10 0 3Ｋ 12ｈ ,空冷 + 10 …     

钛合金电子束焊缝金属微观结构的TEM观察

本文对不同电子束扫描频率的ＴＣ４钛合金焊缝金属微观结构进行了透射电镜观察。研究结果表明,电子束扫描频率对钛合金焊缝金属微观结构有很大影响。电子束扫描作用在焊接凝固前沿的动压力以及焊接凝固过程的稳定性的综合作用,直接影响ＴＣ４钛合金焊缝金属微观结构及位错分布。     

含1.2%铝TRIP钢中残留奥氏体的EBSD研究

残留奥氏体的含量、颗粒尺寸与分布及其稳定性是相变诱导塑性（TRIP）钢获得优良使用性能的关键。马钢试制成功含1.2%铝的TRIP-600钢板,作者用场发射枪扫描电镜EBSD技术对该TRIP钢的残留奥氏体形态、分布与体积分数进行了实验研究。结果表明：实验钢中的奥氏体主要呈细小颗粒状、尺寸在几微米以下,弥散分布于铁素体晶界和晶粒内。EBSD与X-射线衍射测得实验钢板半厚度区的奥氏体体积分数分别为2%和11.4%。本文讨论了EBSD技术测定TRIP钢奥氏体分数引入误差的主要因素。采集图像的步长、试样分析区的选取及试样制备技术等是影响实验结果的重要因素。     

取向硅钢常化处理微观结构的TEM研究

常化工艺是取向硅钢生产工艺的重要一环,合理的常化工艺为随后的冷轧,退火工序创造有利条件,是提高成品磁性的关键工艺.本工作用电子衍衬方法研究3％Si-Fe常化处理后微观结构的变化。采用本工作制订的两段保温常化制度,有助于获得抑制相的理想析出和有利分布,对于抑制初次再晶晶粒长大,完善二次结晶,得到良好磁性,有着重要意义。两段常化工艺,一段是高温1120℃保温2.5分钟,一段是920℃～960℃保温3分钟。主要结果是: 一、抑制相AIN和MnS的析出行为。采用上述两段式保温常化工艺,可明显降低合金的铁损W_(17/50),B_(10)可提高0.01T以上。从920℃到960℃的较宽温度范围内,均可获得大体相同的性能水平,这也正是电镜观察中看到AIN质点析出较多,尺寸比较理想(200～400A)的温度区间,部分热轧试样中也观察到弥散的AIN质点,推测它们是热轧     

Al／20钢爆炸焊接接合区绝热剪切带的TEM观察

绝热剪切现象自４０年代提出以来，人们对它的研究一直没间断过［１，２，３］，但对爆炸焊接接合区出现的绝热剪切带（Ａｄｉａｂａｔｉｃｓｈｅａｒｂａｎｄｓ，即ＡＳＢ）报导较少［４］，尤其是采用ＴＥＭ对爆炸焊接中的ＡＳＢ进行研究的报道更少。本文对工业纯铝／低...     

高氮钢复合焊接接头微观组织及力学性能

为了研究和掌握高氮钢复合焊接接头的微观组织和力学性能,以8mm厚的高氮钢板为试验材料,采用额定功率为4kW的Nd:YAG固体激光器对其进行了激光-电弧复合焊接,利用金相显微镜和扫描电子显微镜对焊接接头的微观组织和断口形貌进行拍照和分析,并利用能谱分析仪和X射线衍射仪,从微区成分元素的种类、含量及物相组成方面进一步分析母材、热影响区、焊缝区的微观组织。结果表明,焊缝区的组织为典型的树枝晶和少量的等轴晶形貌,母材、热影响区都是奥氏体组织,焊缝区除了奥氏体组织外还伴有少量的δ铁素体组织;焊缝中的第二相粒子主要是通过冶金反应产生,以TiO₂、尖晶石（MnAl₂O₄）以及硅酸盐等形式存在,对晶粒有明显的细化作用,可增加焊缝强度;拉伸断裂出现在焊缝区,断口组织形貌为典型的韧窝断裂,并在断裂处可发现有空洞和第二相粒子的形貌特征,说明焊缝缺陷可能导致力学性能薄弱。此研究为激光-电弧复合焊接在高氮钢焊接领域的应用奠定了一定基础。     

低合金相变诱发塑性(TRIP)钢激光焊接的研究进展

系统地总结了低合金相变诱发塑性(TRIP)钢激光焊接的最新研究成果。重点介绍了在激光条件下TRIP钢焊缝中气孔的形成、熔化区的凝固过程、熔化区和热影响区的组织和性能。还介绍了TRIP钢与异种钢板的激光拼焊,TRIP钢的激光切割、激光钎焊和激光点焊。指出了今后TRIP钢激光焊接的研究方向。     

果蝇的透射电镜制样方法研究

果蝇作为一种模式生物,被广泛应用于遗传学、发育的基因调控、人类疾病机制等研究。透射电镜能够观察细胞的超微结构及其变化,是研究果蝇细胞生物学的重要方法之一。本实验研究发现,果蝇样本固定前用双面刀片快速切下头部,固定液能快速有效地固定其体内组织成分,防止内部组织溶解;使用琼脂预包埋果蝇样本,将其修整为长方体,增加其自重,固定其包埋方向,为后续目标位置的超薄切片起到定位作用。     

葡萄石微结构的TEM研究

本文利用电子衍射、电子显微像和晶格像,研究了湖北大治铁山矿床中葡萄石的完整／不完整晶畴、位错、堆垛层镜、复杂界面和斑点状衍射衬度等微结构特征;并从地质温度压力特征、各种电镜现象和葡萄石、绿纤石和多硅白云母晶胞参数特征,探讨了三种矿物形成的纳米拓一向晶格共生的机理。     

Study of the microstructure of IC interconnect metallisations using analytical transmission electron microscopy and secondary ion mass spectrometry

The general goal of this work is to get a better insight in the different microstructural processes taking place in blanket Al(Si)(Cu) metallisations under variable conditions. Using analytical transmission electron microscopy and secondary ion mass spectrometry stable θ-CuAl₂ precipitates are found distributed inhomogeneously in the z-direction of the metallisation with a peak near the substrate side of the metallisation. Additional heating creates larger θ-CuAl2 precipitates distributed inhomogeneously in the z-direction with a peak near the surface of the metallisation as well as in the vicinity of the substrate.     

Computer-assisted simulation of high-voltage electron microscopy using serial images recorded by conventional transmission electron microscopy

Here we describe a computer-assisted method which, based on conventional transmission electron microscopy, renders simulated high-voltage electron micrographs. We perform arithmetic minimum filtering on stacks of aligned serial transmission electron microscopic images. In this way, the structural information of the separate images is fused into one compound image that highlights organization patterns otherwise easily overlooked or impossible to comprehend. Our method, like high-voltage electron microscopy, offers the possibility to build stereo-pairs for high-resolution three-dimensional analysis of tissue layers 1-2 microm thick. The use of background elimination and the development of a depth enhancement routine improved the three-dimensional effect and facilitated the analysis of the interior of objects. As an example, we use the method to display the distribution of axonal organelles at nodes of Ranvier and the shape and contents of a highly branched hippocampal dendritic spine.     

SBT材料微结构的TEM研究

本文利用透射电子显微术(TEM)对 SrBi2Ta2O9 (SBT) 材料(单晶、陶瓷及薄膜)的微结构进行了研究. 在(001)取向的SBT单晶材料及多晶陶瓷中观察到90°铁电畴结构.在SBT晶体中观察到大量的条带状四度反相畴界结构和少量的三度反相畴界结构,利用TaO6氧八面体的扭转和四态自旋结构模型,对反相畴界结构的实验观测结果进行了解释.在(001)取向的SBT铁电薄膜中,观察到小角晶界(倾角为8 2°)的位错分解现象,导致不全位错和层错的出现.利用平衡状态下两个不全位错之间的排斥力等于层错的吸引力,估算了小角晶界处的层错能量,大小为0 27～0 29 J/m2.小角晶界位错的分解对(001)取向的SBT铁电薄膜漏电流及耐疲劳特性具有重要的影响.     

Study of ballistic gold conductor using ultra-high-vacuum transmission electron microscopy

Metal contacts are regarded as key elements of nanometer-scale electronics. Since gold contacts show quantized conductance even at room temperature, much effort has been devoted to understand their conductance behavior on the nanoscale. However, gold contacts do not always show quantized conductance steps during their thinning process, the reason for which has been an open question. Thus, it is necessary to investigate the relationship between the atomic structure and conductance of gold contacts. We developed a custom-made scanning tunneling microscope combined with an ultra-high vacuum transmission electron microscope to clarify the structural dependence of conductance quantization in gold contacts. We found that [111] and [001] gold contacts with a bottleneck shape showed a gradual decrease in conductance with elastic elongation and successive conductance jumps with periodic plastic deformation. In contrast, [110] gold contacts had a hexagonal prism shape (termed gold [110] nanowires). In the conductance histogram, peaks appeared nearly in steps of the quantum unit. We found that the prominent peaks corresponded to stable gold nanowires with a regular hexagonal cross-section. Following first-principles calculations, we confirmed that very thin gold [110] nanowires were ballistic conductors. The conductance behavior differed depending on the contact shape.     

High-resolution transmission electron microscopy on aged InP HBTs

We have used high-resolution transmission electron microscopy (HRTEM), with focused-ion-beam preparation of foils, to study InP HBT devices, both as-fabricated and after aging in life tests. The technology is HRL's G1 process. We found that even after aging for the equivalent of 2 × 10⁷ h under normal operating conditions, the visible damage is extremely benign: the base and emitter contacts are completely intact, there is no evidence of significant Au or Pt migration into the semiconductor, and minor crystal disorder that develops does not extend more than 100 nm below the metal–semiconductor interfaces. Except for these regions, the intrinsic devices are completely devoid of any anomalous features, to within the 0.3 nm resolution limit of the measurements. These observations provide strong evidence that failure mechanisms involving migration of metal from the ohmic contacts, or extended crystal defects, do not limit the reliability of this technology. The small disorder under the base contacts can probably explain the increases of gain (β) observed early in our life tests, and small increases in the base-collector leakage occurring later in the life tests. The minor disorder under the emitter contacts can probably explain the moderate increase of emitter resistance observed late in our life tests. But the mechanism for the eventual decline in β, observed after a long period of stress, for the equivalent of 10⁷ h of normal operation, is not apparent from the HRTEM images.     

Advances in energy-filtering transmission electron microscopy

First experiments using a new energy-filtering microscope (Sub-eV-Sub-A microscope, or SESAM) are shown. They make use of the high transmissivity of the 90 degree filter. This allows the mapping of chemical bonding of large specimen areas, even if narrow energy selecting slits are used. Because large scattering angles are accepted by this filter, energy-filtered diffraction patterns extending to 150 mrad can be recorded by a single exposure. This can be used to determine the reduced density function of amorphous materials and reduces the exposure time of the investigated area by three orders of magnitude as compared with previous approaches.     

Observation of iron silicide formation by plan-view transmission electron microscopy

The formation and the phase transitions of iron silicide by solid-phase epitaxy have been investigated by means of plan-view transmission electron microscopy, which enables us to observe a clean interface between Fe and Si. Layers of Fe were deposited on Si (100) at room temperature in an ultrahigh vacuum chamber. The sample was annealed in the electron microscope at a temperature between 673 and 1073 K. After annealing at 673 K, FeSi crystallites were formed with various orientations. When the annealing temperature was increased to 973 K, we found that the crystallites suddenly started to coalesce into grains of several hundreds of nanometers in size and polycrystalline beta-FeSi2 was formed. These phase transitions were also confirmed with electron energy-loss spectroscopy.